The present invention relates to a work vehicle.
Some conventional work vehicles, such as a tractor and a wheel loader, include a transmission case, to which driving force is transmitted from an engine, provided with a hydraulic mechanical transmission (HMT). In Japanese Unexamined Patent Application Publication No. 2005-83497 that has been filed by the applicants, an inline hydraulic mechanical transmission is proposed in which a hydraulic pump and a hydraulic motor are arranged in series in such a manner that an input shaft of the hydraulic pump and an output shaft of the hydraulic motor are concentrically positioned.
In the inline hydraulic mechanism transmission, the output shaft is fit on the input shaft, to which the driving force is transmitted from the engine, in a relatively rotatable manner. The hydraulic pump, a cylinder block, and the hydraulic motor are fit on the input shaft. The cylinder block is a single unit shared between the hydraulic pump and the hydraulic motor, and is used for transmitting the driving force from the hydraulic motor to the output shaft. Thus, the inline hydraulic mechanical transmission is advantageous over a general hydraulic mechanical transmission in that shifted driving force based on hydraulic pressure and driving force from the engine can be combined to be output, without providing a planetary gear mechanism, so that a high driving force transmission efficiency can be achieved.
The hydraulic mechanical transmission of this type needs to be designed to have a high output to be installed in a work vehicle of a middle or a large size. For example, the high output can be achieved by designing the hydraulic mechanical transmission to have a large capacity. However, a design for simply pursuing the larger capacity leads to a larger hydraulic mechanical transmission not only resulting in a higher manufacturing cost but also compromising the driving force transmission efficiency (efficiency in a low load range in particular).